This is the second revision of an application that proposes to investigate the economic aspects of ecstasy use. This second revision includes all the prior strengths noted by the reviewers, as well as details on how to detect and deal with multicollinearity that makes it difficult to separate the effect of ecstasy from that of other illicit substances. We eliminated one specific aim as recommended. There are many other smaller changes in this revision, demarcated by italics throughout this application. For many years ecstasy has had a deceptive reputation as a "safe" drug, but recent research has evidenced its adverse physiological and psychological effects on human health. Little research has however examined the economic aspects of ecstasy use. This study proposes to (1) Estimate the extent to which ecstasy contributes to higher utilization and cost of health services among adolescents (ages 12-17 years) and young adults (ages 18-34 years);(2) Estimate the extent to which ecstasy contributes to crime/delinquency activities among adolescents (ages 12-17 years) and young adults (ages 18-34 years);(3) Investigate the relationships between ecstasy and academic performance among high school students (grades 9 to 12);and (4) Examine the extent to which polydrugs differentially affect the economic aspects of ecstasy. These aims will be addressed by analyzing the following recent public use datasets: the 2002, 2003, and 2004 National Survey on Drug Use and Health (N=164,902) and the 2001, 2003, and 2005 school-based Youth Behavior Risk Survey (N=42,613). Ecstasy users may generate private and social costs through utilization of more costly emergency services and/or hospitalizations and involvement in crime/delinquency activity. To the extent that high school academic performance affects future job opportunities, the impact of ecstasy on high school academic performance will have far-reaching human capital consequences. This project will be the first broad national research of economic aspects of ecstasy use. Insights from the study will influence policies that encourage more ambulatory care, lower involvement in crime delinquency, and improved employment opportunities. Policy makers, clinicians and other health care providers, public health organizations, substance abuse program personnel, law enforcement personnel, school managers, and family members will use findings from this study as they decide how to develop cost-effective treatments as well as programs to identify and divert future Ecstasy Users to prevention programs. The bridge between research, policy, and practices has yet to be successfully established. We are committing to disseminate these findings to the widest audience possible, through professional conferences, policy workshops, and other distribution channels such as school/college-based venues and community-based treatment programs.